Means and method for eliminating background noise in recording sound



May 11, 1937. R. 5. FEAR 2,079,959

MEANS AND METHOD FOR ELIMINATING BACKGROUND NOISE IN RECORDING SOUNDFiled Nov. 17, 1934 2 Sheets-Sheet l 4- 9 Q 2 m m: AMPLIFIER H 27 3 ELII 5 RECORDER 9 1s IDEMHENETlZE R m I6 14 EU 1 F T UF' I'l'l AMPLIFIERAMPLIFIER INVENT OR.

May 11, 1937. R G FEAR 9 2,079,959

MEANS AND METHOD FOR ELIMINATING BACKGROUND NOISE IN RECORDING SOUNDFiled Nov. 1'7, 1934 2 Sheets-Sheet 2 illllli jili w I 1|| m :1

p n i in 1 73 74 I INVENTOR.

Patented May ll, 1937 umreo STATE-S PATENT OFFICE MEANS AND METHOD FORELIIWINATING BACKGROUND SOUND NOISE IN RECORDING My invention relates-toa method for eliminating back ground noise in recording sound, moreparticularly to a new andnovel means foreliminating back ground noisewhen sound is recorded for use with motion pictures.

Hence one of the purposes of my invention is to provide means and methodfor eliminating back ground noise in sound recording.

Another object ofmy invention is to eliminate back ground noise in soundon wax or photographic type of recording.

Another object of my invention is to provide a time delay means, wherebyan original sound may be delayed or stored electromagnetically orotherwise for a period of time sufilcient to enable controlling means tobe actuated during such time delay.

All of these objects and others will appear to those skilled in the artof sound recording and 9 can be better understood by reference to theappended specification and drawings wherein like numerals indicatecorresponding parts in the several views. r

Referring to the drawings.

Figure 1 is a diagrammatic view of the apparatus used to accomplish mypurposes;

Figure 2 is an enlarged front elevation of the electromagneticallyoperated shutter;

' 'Figure 3 is a side elevation thereof;

30 Figure 4 is a diagrammatic view of the apparatus when used upon aphonographic disc recorder; and

Flgurefi isa vertical section taken'on the line 5-5 of Figure 4.

35 The several views illustrate one method of accomplishing my purposewherein the means used is to translate sound or a record of sound into.varying electrical currents, to amplify said electrical' currents byconventional means such as by a vacuum tube amplifierfand then tomagnetically record such electrical impulses upon a steel wire, belt ordisc.

This is done by passing an endless steel wire belt, or disc moving at aconstant speed between 4 two poles of an electric magnet.

This can be better understood by referring to Figure 1 where is shown amicrophone i, the

output electrical current of which is fed by means of wires 2 and 3 intothe amplifier 4, wherein the electrical currents generated by themicrophone are amplified to a degree suitable for actuating theelectromagnet 5, which is actuated by the amplified electrical currentsthat pass out of the amplifier 4 and thru feed wires 8 and An endlesssteel wire or belt 8 passes between the poles 9 and Ill of the aforesaidmagnet and then around the two pulleys H and [2, one of which may bedriven at a constant speed by any suitable means, not shown.

In the diagram (Figure 1) the endless steel wire or belt 8 is shown aspassing around pulley H, then between pole pieces 9 and ill of themagnet 5, then around pulley l2, after which it passes thru and betweenthe pole pieces l3 and l of the second electromagnet l5, then betweenpole pieces l6 and ll of a third electromagnet 18, then it passes thruanother electromagnet l9 having pole pieces and 2|, after which it againengages pulley H thus completing the travel cycle aroundthe two-pulleys.

The electromagnet i5 is connected to wires 22 and 23, which areconnected to amplifier 24, wherein electrical currents generated by theelectromagnet I5 are suitably. amplified. 4

Wires 25 and 26 feed the output of the amplifier to theelectromagnetically operated shutter 26a.

Referring to Figure 2:

'The electromagnetically operated shutter 260. has coils 21 and 28 thathave cores terminating in pole pieces 29 and 30 and slots 3| and 32 intowhich the shutter leaves 33 and 34 are fitted. This shutter 26a beingelectrically operated only when a sound is recorded on the wire 8prevents any noise to enter the recorder.

Referring to Figure 3 Frame 35 supports the two coils 21 and 2B, and

-is arranged with a hinge pin 36 to support the two shutter blades 33aand 34a. Springs 31 and.

.38 held to the frame 35 by screws 39 and 40 which hold the shutter in anormal closed position when the mechanism is not operating.

Again referring to Figure 1: i The electromagnet pick up i8, feedscurrent thru wires 4| and 42 into amplifier 43, where the varyingcurrents generated by the pick-up 18 are amplified.

These amplified currents feed the light valve M, which maybe ofidentical construction to the magnetically actuated shutter 26a as shownin Figures 2 and 3.

An exciter lamp 45 which may burn at a constant intensity has acondenser lens 46 that focuses light onto the shutter of the lightvalve.

An objective lens 41 is arranged to pick up the light metered thru theshutter of the light valve and focus this metered light into the filmrecorder 48.

of film 50 is supported upon a spindle 5| and is led'down into therecorder where it engages with feed sprocket 52, being held thereon byholding means 58, after which it is led to recording sprocket 54, uponwhich it is held by engaging means 55. After leaving sprocket 54, thefilm 50 is led under tension roller 56, over guide roller 51, overrecording shoe 58 and roller 59 and back onto recording sprocket 54,being held thereon by film sprocket engaging means 60, after which it isagain led back onto feed sprocket 52, being held thereon by filmengaging means 6|, and after leaving the feed sprocket 52 it is led orpulled out of the recorder by take up spindle 62 of the magazine 9.

The recorder may be mounted upon a base 63, and driven by a motor 64arranged to rotate ata constant speed.

The operation of my invention as described in the above mentionedcombination of elements, still referring to Figure 1, is as follows.

The microphone 8 picks up sound and converts the sound waves intoelectrical impulses. These are amplified by the amplifier 4, and

energize electromagnet 5 which in turn mag-- netizes the wire or belt 8as it passes thru the aforesaid magnet and records sound thereon.

The wire 8 then passes around pulley l2 and between the poles of theelectromagnet I 5 and the sound recorded upon said wire energizes saidmagnet, which then becomes a magnetic pick-up, causing electricalcurrents to flow into the amplifier 24. These currents are thenamplified by the amplifier 24 to a degree powerful enough to actuate arelay and cause it to close. This relay which is embodied within thecase of the amplifier 24, closes an electrical circuit powerful enoughto actuate the electromagnet 26 and cause the shutter blades 33 and 34to fly open./

The relay within amplifier is adjusted so that it will remain open aslong as it is energized by any sound that may have been recorded uponthe wire 8, which in turn is picked-up by the magnet l5, and sothat itwill close when there is no recorded sound upon the wire 8.

As it takes a small fraction of time for the relay mechanism and theshutter mechanism 26a to operate, the re-recording pick-up I8 is locatedat a point remote enough so that the aforementioned mechanisms can beactuated by the-recorded sound before the sound recorded upon the wirepasses into the electromagnetic pick-up l8.

When the sound recorded upon the wire has passed by the electromagnetl5, causing the magnetically operated shutter to open, and passesbetween the pole pieces l6 and ll of the magnetic pick-up 18, it causeselectrical currents to be generated in the electromagnetic pick-up l8,and these currents after being amplifiedby the amplifier 43 actuate thelight valve 44, thus metering the light emanating from the exciter lamp45 and thus re-recording the sound, that had heretofore been recordedupon the steel wire, upon the film passing thru the film recorder.

After the sound recorded upon the wire 8 passes the pick-up l8, itpasses between the poles of the electromagnet l9;

This magnet I 9 is energized by a battery 65 and mum magnetic record toaffect the magnetic relay or this same condition may be adjusted in theamplifier 24 so that the shutter 26d will normally remain closed andonly open when sound of a definite intensity has been recorded upon thewire. Hence it is possible to entirely eliminate any recording of lowlevel sound that may havev been picked up by the microphone.

In the foregoing I have illustrated and described my invention when usedto control the recording that is being done by a metering light valve,but it is obvious that a glow lampmay be substituted with equallysatisfactory results.

My invention may-be used and actuated by recording from a wax recordsuch as illustrated in Figure4 with exactly the same results.

It will be obvious that any degree of time delay desired may be securedby the above arrangement and that it is not necessary to synchronize thewire or disc recording mechanism with the recorder or its associatedapparatus.

Referring to Figure 4.

The wax disc 66 is placed in the usual manner on a phonograph machinehaving uprights 61 and 68 the which the screw driving shaft 69 passesand at oneend of said screw driving shaft is attached the worm gear 10actuated by worm H journalled in bracket I2 secured to the upright 61.This worm ll meshes with worm gear 13 secured on the driving shaft 14 ofthe motor 15, which driving shaft 'also operates the wax disc 66 at aconstant speed.

A rod 83 is secured to the uprights 61 and 88 on which the recordermeans to move as well as to steady the said movement.

The arm 17 carrying the pick-up I8 is pivotally secured at 84 to theframe of the machine and at the other end of said arm being providedwith a hinged portion 19 to which the pick-up l8 means is attached.

A similar arm 80 carrying the noise reduction shutter pick-up 26apivotally secured at 85 to the frame of the machine and at the other endof said arm being provided with a hinged portion 82 to which the noisereduction shutter pick-up is attached.

The wiringof these several parts are similar to the wiring descriptionofFigure 1.

While the details of the means and method for securing noise reductionin recording sound have I .been specially described in Figure 1, and oneof the modified forms of construction shown in Figure 4, this inventionis not confined thereto as other changes and modifications may be madewithout departing from the spirit and scope of my invention as definedby the appended claims.

What I claim is:

1. In an apparatus of the characterdescribed, a moving sound recordmedium, means for magnetically recording sound on the record medium, anelectro-magnetle pickup-amplifier-relay operated shutter cooperativewith the record medium and adapted to operate at a predeterminedsoundintensity, and a second electromagnetic pickupamplifler-light valverecorder, also cooperative with said record medium for re-recording thesound on a second record medium. I

2. The apparatus as set forth in claim 1,.wherein the said secondelectromagnetic pickup is spaced from the first named electromagneticpickup at a distance therefrom corresponding to a time delay intervalnecessary for of the amplifier-relay operated shutter.

3. The apparatus as set forth in claim 1, wherein a means is providedfor de-magnetizing the the operation moving sound record mediumfollowing the sound re-recording 'operation.

4. The apparatus as set forth in claim 1, wherein the said movable soundrecord medium is in v 5. The apparatus as set forth in claim'l, whereinthe said moving sound record medium is in the form 01 an endlessflexible metal member and a means is provided to impart motion to themember at requisite speed for the effective re- 5 cording andre-recording of sound.

RALPH GORDON FEAR.

